Ординатура / Офтальмология / Английские материалы / Cataract Surgery in the Glaucoma Patient_Johnson_2009

devices in combination with cataract extraction, early results show promise in their efficacy in lowering IOP as well as decreasing dependence on topical medications. Although IOP lowering with these devices may not achieve targets as low as traditional trabeculectomy, the risk profile of these procedures appears to be significantly more favorable and physiologic in their mechanisms of IOP reduction. This has afforded patients the option of undergoing surgery that has a lower risk profile, possibly at an earlier juncture of disease, providing IOP control before the patient develops disease that requires excessively low target IOPs. Patient selection, therefore, is critical in choosing the appropriate procedure if considering a new glaucoma device. Each case should still be considered as a unique situation and in order to maximize success and IOP control, the clinical judgment of the surgeon is critical in determining the amount of IOP reduction required, balanced with the acceptable risk to the patient (Fig. 14.44).

References

1.Stocker F. Combined cataract extraction and scleral cauterization.

Arch Ophthamol. 1964;72:503.

2.Boyd F. Filtering cautery sclerostomy combined with cataract extraction. Highlights Ophthamol. 1968;11(1):39–77.

3.Maumenee A, Wilkinson CP. A combined operation for glaucoma and cataract. Am J Ophthamol. 1971;69:360.

4.Dellaporta A. Combined trepano-trabeculectomy and cataract extraction. Trans Am Ophthalmol Soc. 1971;69:113–23.

5.Cairns J. Trabeculectomy. Preliminary report of a new method. Am J Ophthalmol. 1968;66(4):673–9.

6. Bindlish R, Condon GP, Schlosser JD, DAntonio J, Lauer KB, Lehrer R. Efficacy and safety of mitomycin-C in primary trabeculectomy: five-year follow-up. Ophthalmology. 2002 Jul;109(7):1336–41.

7.Palmer S. Mitomycin as adjunct chemotherapy with trabeculectomy. Ophthalmology. 1991 Mar;98(3):317–21.

8.Follow-Up FFSSo-y. The Fluorouracil Filtering Surgery Study Group. Am J Ophthalmol. 1989 Dec 15;108(6):625–35.

9.Kupin T, Juzych MS, Shin DH, Khatana AK, Olivier MM. Adjunctive mitomycin C in primary trabeculectomy in phakic eyes. Am J Ophthalmol. 1995 Jan;119(1):30–9.

10.Borisuth N, Phillips B, Krupin T. The risk profile of glaucoma filtration surgery. Curr Opin Ophthalmol. 1999 Apr;10(2): 112–6.

11.Poley B, Lindstrom RL, Samuelson TW. Long-term effects of phacoemulsification with intraocular lens implantation in normotensive and ocular hypertensive eyes. J Cataract Refract Surg. 2008;34:735–42.

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13.Coupin A, Li Q, Riss I. Ex-PRESS Miniature Glaucoma Implant Inserted Under a Scleral Flap in Open-Angle Glaucoma Surgery: A Retrospective Study. Fr J Glaucoma. 2007 Jan;30(1):18–23.

14.Dahan E, Carmichael TR. Implantation of a Miniature Glaucoma Device Under a Scleral Flap. J Glaucoma. 2005;14(2):98–102.

15.Maris P, Ishida K, Netland PA. Comparison of Trabeculectomy with Ex-PRESS Miniature Glaucoma Device Implanted Under Scleral Flap. J Glaucoma. 2007 Jan;16:14–9.

16.Sarkisian SJ. Use of an injector for the Ex-PRESS Mini Glaucoma Shunt. Ophthalmic Surg Lasers Imaging. 2007 Sep– Oct;38(5):434–6.

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PRESS Miniature glaucoma devices: case series and technique for tube shunt removal. J Glaucoma. 2007 Dec;16(8):704–6.

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22. Koslov V, Bagrov SN, Anisimova SY, et al. [Nonpenetrating deep sclerectomy with collagen][Russian]. Oftalmokhirurgiia 1990;3:44–6.

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25.Stegmann R, Pienaar A, Miller D. Viscocanalostomy for open angle glaucoma in black African patients. J Cataract Refract Surg. 1999;25:316–22.

26.Sourdille P, Santiago P-Y, Villain F, et al. Reticulated hyaluronic acid implant in nonperforating trabecular surgery. J Cataract Refract Surg. 1999;25:332–9.

27.Ambresin A, Shaarawy T, Mermoud A. Deep sclerectomy with collagen implant in one eye compared with trabeculectomy in the other eye of the same patient. J Glaucoma. 2002;11:214–20.

28.Sanchez E, Schnyder CC, Sickenberg M, et al. Deep sclerectomy: results with and without collagen implant. Int Ophthalmol. 1996/97;20:157–62.

29.Spiegel D, Kobuch K. Trabecular meshwork bypass tube shunt: initial case series. Br J Ophthalmol. 2002;86:1228–31.

30.Yablonski M. Trabeculectomy with internal tube shunt: a novel glaucoma surgery. J Glaucoma. 2005;14:91–7.

31.Grant W. Further studies on facility of flow through the trabecular meshwork. AMA Arch Ophthal. 1958;60(4 part 1):523–33.

32.Ethier C, Kamm RD, Palaszewski BA, et al. Calculations of flow resistance in the juxtacanalicular meshwork. Invest Ophthalmol Vis Sci. 1986 Dec;27(12):1741–50.

33.Rosenquist R, Epstein D, Melamed S, et al. Outflow resistance of enucleated human eyes at two different perfusion pressures and different extents of trabeculotomy. Curr Eye Res. 1989;8(12):1233–40.

34.Moses R, Grodzki WJ Jr, Etheridge EL, et al. Schlemm’s canal: the effect of intraocular pressure. Invest Ophthalmol Vis Sci. 1981;20(1):61–8.

35.Lewis R, von Wolff K, Tetz M, et al. Canaloplasty: circumferential viscodilation and tensioning of Schlemm’s canal using a flexible microcatheter for the treatment of open-angle glaucoma in adults: interim clinical study analysis. J Cataract Refract Surg. 2007 Jul;33(7):1217–26.

36.Shingleton B, Tetz M, Korber N. Circumferential viscodilation and tensioning of Schlemm canal (canaloplasty) with temporal clear corneal phacoemulsification cataract surgery for open-angle glaucoma and visually significant cataract: One-year results. J Cataract Refract Surg. 2008;34:443–40.

37.Gramer E, Tausch M, Kraemer C. Time of diagnosis, reoperations and long-term results of goniotomy in the treatment of primary congenital glaucoma: a clincal study. Int Ophthalmol. 1996;20:117–23.

38.Luntz M, Livingston DG. Trabeculotomy ab externo and trabeculectomy in congenital and adult-onset glaucoma. Am J Ophthalmol. 1977;83:174–9.

39.Herschler J, Davis EB. Modified goniotomy for inflammatory glaucoma. Histologic evidence for the mechanism of pressure reduction. Arch Ophthalmol. 1980;98:684–7.

40.Dickens C, Hoskins HD Jr. Epidemiology and pathophysiology of congenital glaucoma. In: Ritch R, Shields MB, Krupin T, eds. The Glaucomas. Vol. 2, 2nd ed. St. Louis: Mosby; 1996: 729–38.

41.Jacobi P, Dietlein TS, Krieglstein GK. Technique of goniocurettage: a potential treatment for advanced chronic open angle glaucoma. Br J Ophthalmol. 1997;81:302–7.

42.Hill R, Baerveldt G, Ozler SA, et al. Laser trabecular ablation (LTA). Laser Surg Med. 1991;11:341–6.

43.Epstein D, Melamed S, Puliatio CA, Steinert RF. Neodynium: YAG laser trabeculopuncture in open-angle glaucoma. Ophthalmology. 1985;92:931–7.

44.Spiegel D, Garcia-Feijoo J, Garcia-Sanchez J, Lamielle H. Coexistent primary open-angle glaucoma and cataract: preliminary analysis of treatment by cataract surgery and the iStent trabecular micro-bypass stent. Adv Ther. 2008;25(5):453–64.

45.Zhou J, Smedley GT. A trabecular bypass flow hypothesis. J Glaucoma. 2005;14(1):74–83.

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49.Francis B, Minckler D, Dustin L, et al. Combined cataract extraction and trabeculotomy by the internal approach for coexisting cataract and open-angle glaucoma: Initial results. J Cataract Refract Surg. 2008;34:1096–103.

50.Minckler D, Baerveldt G, Ramirez MA, et al. Clinical results with the trabectome, a novel surgical device for treatment of open-angle glaucoma. Trans Am Ophthalmol Soc. 2006;104:40–50.

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Introduction: Update on Exfoliation Syndrome

Exfoliation syndrome (XFS) was first described in 1917 by the Finnish ophthalmologist John Lindberg1 and currently affects 60–70 million people worldwide.2–4 Of these, 15–17 million have increased intraocular pressure (IOP) and 5–6 million are estimated to suffer from exfoliative glaucoma (XFG), a form of secondary open-angle glaucoma that develops as a consequence of XFS and is considered the most common identifiable cause of open-angle glaucoma worldwide.2 Its aggressive course and worldwide prevalence makes it critical for ophthalmologists to be familiar with the full clinical spectrum of the disease.5–10 However, significant barriers to the successful diagnosis and management of

XFS and XFG still exist. As XFS is a slowly progressive disease with subtle signs, early diagnosis is difficult.3,7,9,11

Indeed, the condition may remain undetected until the clinical signs become more apparent or when cataract or XFG develop. With increasing life expectancy, it is important that efforts are focused on improving the management of patients with exfoliation and alleviating the burden of visual loss and

complications during cataract surgery in patients with XFS and XFG.7,8

discovery in 2007 of the role played by lysyl oxidase-like protein 1 (LOXL1) gene polymorphism in the development of the condition has shed more light on its genetic background.13 LOXL1 is a member of a gene family that plays an important role in elastin metabolism. Specific mutations of the LOXL1 gene are strongly associated with the development of XFS and XFG. It is hypothesized that dysfunction of the LOXL1 gene may lead to the progressive accumulation exfoliation material. This may explain the histological findings and several XFS-related complications.12

Ultrastructurally, exfoliation deposits consist of electron dense, fibrillar, elastotic material.5 Histochemically, XFM consists of a core protein surrounded by glycoconjugates, giving it a glycoprotein/proteoglycan structure.5,6,12 Exfoliation aggregates can be seen both intracellularly during synthesis, and as extracellular deposits. Though intraocular and extraocular deposits are not morphologically or biochemically identical, both represent the same type of abnormal fibrillopathy.12 Recent data suggest that the exfoliation-related biochemical changes are influenced by increased oxidative stress,14 which as a part of a vicious circle, is enhanced by the exfoliation-induced tissue damage. Development of nuclear cataract is more common in patients with XFS/XFG and may

be related to the increased oxidative stress in the anterior segment of the affected eye.3,14

Pathophysiology

Both XFS and XFG are age-related conditions characterized by the systemic synthesis and progressive accumulation of a fibrillar extracellular material (exfoliation material) in many ocular and systemic tissues. Exfoliation material synthesis may relate to disturbed elastin metabolism.12 The

A.G.P. Konstas ( )

AHEPA Hospital, 1st University Department of Ophthalmology, Thessaloniki 54636, Greece

e-mail: konstas@med.auth.gr

Clinical Implications

Exfoliation material is not only synthesized and accumulated in different tissues, but by disturbing extracellular matrix metabolism it can induce alterations in function. These XFSrelated degenerative changes are clinically important, may

result in surgical complications during phacoemulsification surgery,11,15,16 and, consequently, must be known by all

ophthalmologists. Prevention of surgical complications in cataract surgery is a key aim of successful XFS management.

Existing evidence shows that XFS is an important risk factor for vitreous loss.3,7,9,11 Although the ultimate impact of

XFS/XFG in cataract surgery is currently not known (since there are limited controlled data on the subject) there is some evidence to show that detection of exfoliation signs in the cataract patient, together with the appropriate management during surgery, can improve surgical outcome.

On routine biomicroscopic examination of the eye,

without dilatation of the pupil, the diagnosis of XFS can be missed5,11 and the prevalence can be underesti-

mated.4,9 The diagnostic sensitivity increases when the condition is sought by an experienced observer who is fully aware of the full diagnostic spectrum of the disease.7 See Table 15.1. Although the clinical description of fully developed XFS is well established, little is known about the early changes, which are less well defined.17 For example, exfoliation aggregates can be identified by transmission electron microscopy within eyes in which it is not clinically apparent.10,17 These factors result in an artificially low prevalence of the condition. More efficient diagnostic techniques and a new classification scheme may be key components in improving detection in the future.

Table 15.1 Clinical manifestations of pseudoexfoliation

•Cataract

•Exfoliation aggregates on anterior segment tissues

•Poor dilation

•Weak zonules/zonular laxity

•Glaucoma

•Corneal endotheliopathy

•Possibly vascular disease

Although not well described, there appears to be a significant association between XFS and cataract formation. There is a high prevalence of XFS in eyes coming to cataract

surgery and a high prevalence of cataract in eyes with XFS7,15,16 compared with age-matched eyes without XFS.

The etiologic relationship between the two disorders remains unclear. Koliakos et al.14 observed a significantly reduced level of ascorbic acid in the aqueous humor of patients with XFS. Since ascorbic acid plays an important role in protecting the lens from ultraviolet irradiation, this finding may provide a logical explanation for the greater incidence of cataract formation and posterior capsular opacification after cataract extraction in eyes with XFS.

The clinical diagnosis of XFS or XFG is based on the incidental finding of “dandruff-like” exfoliation material upon the pupillary margin, or “sugar frosting” of the anterior lens capsule.2,3 Generally these are the most consistent signs of the condition. In the fully developed condition,3 complete or sometimes incomplete distinct exfoliation zones may be visualized after pupillary dilatation: a relatively homogeneous, subtle central disc corresponding to the diameter of the pupil; a granular, often layered, peripheral zone; and a clear intermediate area separating the two (Fig. 15.1). Several variations may arise, however, due to the differences in the

Fig. 15.1 A slit lamp photo of a dilated pupil revealing the lens with the zones associated with pseudoexfoliation syndrome. Courtesy of Tom Monego, Dartmouth Hitchcock Medical Center (DHMC), Lebanon, NH

quantity and rate of deposition of exfoliation material, different stages in the disease process, and the varied anatomic relationship and proximity of the posterior iris surface to the anterior lens.5,7 The peripheral granular zone is thought to be a pathognomonic clinical sign and thus the most reliable sign assisting the diagnosis. Early in the course of the disease, subtle striations of exfoliation material and/or pigment “sunflower” deposits may be discerned on the surface of the lens.3 The diagnosis of the condition is more difficult in the presence of cataract. In a histological study, XFS was diagnosed in 33% of cataractous lenses, whereas only 16% of the cases had been diagnosed clinically prior to cataract surgery.18 After cataract extraction, exfoliation material may be found deposited upon the anterior vitreous face or on vitreous strands when the face is ruptured, on the posterior cap-

sule, and on intraocular lenses, indicating that the presence of the lens is unnecessary for its continued formation.2,9,10

Exfoliation deposits may be detected early on the ciliary processes and zonules. Zonular aggregates may in fact predate the development of the peripheral granular zone upon the lens surface.5,6 It is well documented that XFS can cause zonular fragility, which may lead to lens subluxation and surgical complications during phacoemulsification. The zonules are sometimes heavily coated with exfoliation material and, in extreme cases, severely damaged and broken.9 An additional mechanism may also be the degeneration induced to the zonular attachments to the lens, or ciliary body. Currently, the zonular fragility, thinning of the equatorial lens capsule, and reduced dilation of the pupil in XFS are thought to be responsible for the increased complication rate during cataract surgery, as well as the postoperative decentration of intraocular lenses even years after uncomplicated cataract surgery.9 In a small number of cases, exfoliation-induced corneal degenerative changes may impact the number and

shape of corneal endothelial cells, which may ultimately lead to corneal decompensation5 even after uncomplicated phacoemulsification, or following marked elevation of IOP.11

Degenerative ischemic changes in the iris are also induced by XFS and result in reduced pupillary dilatation. These changes induced by massive exfoliation deposits around iris vessel walls lead to micro-occlusions, formation of ghost vessels, and secondary micro-neovascularization.3,5,12 These ultrastructural and functional alterations result in increased vascular permeability and impairment of the blood-aqueous barrier function, which can lead to increased incidence of posterior synechiae formation and a higher incidence and duration of inflammation after intraocular surgery.

Retrobulbar perfusion may also be impaired in XFS and XFG.8,9

There is evidence to suggest that XFS is a systemic dis-

order.19–21 Patients with XFS may exhibit systemic vascular involvement20,21 and it has been postulated that XFS

may contribute to increased morbidity. There are reports of impaired regulation of heart function and reduced precapillary perfusion.20 There are conflicting reports suggesting an increased prevalence of ischemic heart disease in XFS, but the prevalence of diabetes mellitus is only half of that seen in age-matched controls or in patients with primary open-angle glaucoma and there is no evidence that XFS/XFG lead to increased mortality.19 Further controlled evidence is required to elucidate the precise systemic risk induced by XFS.

Elevated IOP with or without glaucomatous damage occurs in approximately 25% of people with XFS or about 6–10 times the rate in eyes without XFS.6–10 When XFG develops, it is associated with worse untreated 24-h IOP characteristics and a worse prognosis than primary open-angle glaucoma.22,23 Due to the unfavorable pressure characteristics, more aggressive medical therapy is needed and it is generally more difficult to reach the predetermined target IOP in XFG.11,23 Thus, adjunctive medical therapy, laser treatment, and surgery are more often necessary in XFG. However, the best first-line and stepwise therapy in XFG remains controversial.11 Therefore, it is important to determine in the future the optimum choices for successful therapy in XFG.

Intraocular Pressure Changes After Phacoemulsification in Eyes with XFS

The common coexistence of cataract and raised IOP in XFS often poses management dilemmas concerning the optimal surgical approach. Accurate estimation of the magnitude of potential IOP reduction in response to cataract surgery in XFS or XFG would be useful in determining whether to do phacoemulsification alone or combine

the surgery with trabeculectomy. Several studies have noted a decrease in IOP following phacoemulsification in eyes with and without XFS.24–27 A number of studies were retrospective and have examined the effect of phacoemulsification on IOP levels in patients with and without XFS. Suzuki et al.28 reported a decrease in IOP after surgery in patients without preexisting disease. Patients with increased preoperative IOP with or without glaucoma but no XFS may also exhibit meaningful postoperative IOP drops.25,29 Three studies have reported that XFS patients with a normal preoperative IOP manifested a decrease in IOP postoperatively that was significantly greater than similarly matched

controls without XFS, with the effect sustained up to a 2-year follow-up.26,30,31 In the study by Merkur et al., postoperative

IOP changes from baseline in the XFS group were –1.8, –4.5, and –2.3 mmHg at 3, 6, and 12 months, respectively. In the study by Shingleton, IOP declined from a mean of 16.8 to 13.9 mmHg in the XFS group and from 16.3 to 14.4 mmHg in the control group at 2 years.34

These observations have been confirmed in a large prospective multicenter cohort study by Damji et al.32 This study demonstrated that patients with XFS have a greater IOP lowering effect following phacoemulsification than those without XFS. The IOP reduction was significantly greater in the exfoliation group at all time points out to 2 years. In the subgroup analyses, IOP lowering was –1.85 mmHg at 2 years in the XFS patients versus –0.62 mmHg in the controls. Importantly, patients with XFG also exhibited a more pronounced IOP lowering than those with POAG (–3.15 mm versus –1.54 mmHg, respectively) after 2 years. It is interesting that the IOP lowering effect in the XFS group was closely related to the irrigation volume utilized at the time of surgery. The authors speculated that this may be because of one or more of the following factors: washing out of exfoliation material and pigment from the anterior segment, deepening of the anterior chamber angle, and lowgrade inflammation leading to enhanced aqueous outflow.

It has been argued that patients with XFS undergoing phacoemulsification experience a greater decrease in IOP postoperatively in comparison with patients without XFS because phacoemulsification eliminates iridolenticular friction and thus significantly reduces the release of pigment from the iris and exfoliation material from the lens and iris. The procedure also removes loose exfoliation material and pigment from the clogged outflow system, and thus

may lead to further IOP lowering in patients with XFS or XFG.33,34 It has been hypothesized that the removal

of exfoliation material and pigment is the mechanism for this recorded IOP lowering with subsequent improved outflow. The term “trabecular aspiration” (TA) was introduced by Jacobi and Krieglstein in 1994, who employed a special aspiration system.33–35 Trabecular debris and pigment was cleared with a suction force of 100–200 mmHg.

They concluded that trabecular aspiration combined with phacoemulsification was significantly more effective than cataract surgery alone in reducing postoperative IOP and the necessity for anti-glaucoma medications, but not as effective as phacotrabeculectomy. Cimetta et al.36 performed phacoemulsification with exfoliation material aspiration with IOP reduction lasting up to 1 year postoperatively. Other possibilities that contribute to IOP lowering include upregulation of matrix metalloproteinases, biochemical or blood-aqueous barrier alterations with release of prostaglandins,37 or other physiological processes that alter and improve trabecular or uveoscleral outflow.

Whether to perform cataract surgery alone or combine it with a trabeculectomy is an important clinical decision when treating patients who have XFG and a visually significant cataract. The advantages of a combined procedure are the prevention of IOP spikes and better long-term IOP control postoperatively. However, combined cataract surgery and trabeculectomy in XFG may lead to a higher rate of complications including hypotony, suprachoroidal hemorrhage, and endophthalmitis.

The data being accumulated to date are consistent with the notion that in many patients with early to moderate XFG, phacoemulsification alone is a reasonable option for better IOP management. This approach has the advantage of faster visual rehabilitation and fewer surgical complications. How long the beneficial effect of cataract surgery on IOP lowering lasts is currently unknown and merits further investigation.

Preoperative Examination

In most cases, exfoliation material can be observed with careful slit-lamp examination after pupil dilatation, even in the early stages of XFS. The presence of XFS or XFG poses an increased risk during and after cataract surgery, particularly if undetected. Zonular weakness and poor trabecular outflow with elevated IOP may pose specific intraoperative problems. Hence, preoperative documentation of XFS, which often may otherwise go undetected, is key to successful cataract surgery. Signs indicative of weak zonules are listed in Table 15.2. However, only slight phacodonesis andor an iridolenticular gap may be seen. Kuchle et al.47 found a correlation between a shallow anterior chamber and zonular instability, which indicates that reduced anterior chamber depth with normal axial length should alert the surgeon to possible zonular laxity. Reduced chamber depth in a highly myopic eye is virtually pathognomonic of zonular laxity. It is important to study anterior chamber depth when seated and lying prone, since this would give a measure of zonular laxity, particularly after paralysis of accommodation. In patients with XFG elevated IOP, especially in elderly patients, may increase the risk of perioperative complications and, specifically, increase the risk of choroidal hemorrhage.53

Table 15.2 Signs of weak zonules

•Distinct phacodonesis

•Iridodonesis

•Vitreous prolapse

•Lens subluxation

•Shallow anterior chamber

Operative Techniques and Considerations for Phacoemulcification in Eyes with XFS

Cataract surgery in the presence of XFS is generally considered to be a challenge as it has been associated with an increased incidence of intraoperative complications. The

risks were first described for extracapsular cataract extrac- tion38–43 and later for phacoemulsification.30,44–47 In XFS,

lysosomal proteinases destroy the normal basement membrane structure of the non-pigmented epithelium of the ciliary body and anterior lens capsule. This loosens the zonule– lens capsule complex and causes adhesions between the zonules and non-pigmented epithelium.9,48 The rotational and antero-posterior forces created during surgery may lead to total separation of these weakened zonules, resulting in vitreous loss. As discussed previously, other factors thought to contribute to the increased incidence of intraoperative complications during cataract surgery in eyes with XFS are a poorly dilating pupil, corneal endothelial changes, and blood–aqueous barrier breakdown.49–52

Management of Small Pupil in XFS

A small pupil is a problem frequently encountered during phacoemulsification in eyes with XFS. Maximal pupil dilatation is significantly less in XFS eyes compared to normal eyes.30 Mechanical dilatation of the smallest pupils (e.g., <4 mm in diameter) is an efficient and commonly used technique, although it may lead to micro-ruptures of the

sphincter, increased postoperative inflammation, and, sometimes, result in a permanently dilated pupil.41,54,55 In these

cases, bimanual stretching with Y-hooks, iris retractor hooks (Fig. 3.4), Beehler pupil dilator (Fig. 3.3), or polymethylmethacrylate (PMMA) pupil dilator rings (Figs. 3.5, 3.6, 3.7 and 3.8) are useful. Akman et al.56 compared these four methods of pupil dilatation in XFS eyes undergoing phacoemulsification and concluded that all of them were effective. The two most time consuming devices, iris retractor hooks and PMMA pupil dilator rings, were also best at keep-

ing the pupil dilated during surgery. The dilator ring caused the least iris trauma. See also Chapter 3.

Surgical Considerations in the Presence

of Zonular Weakness

Capsulorrhexis and Hydrodissection

It is important to avoid overinflating the anterior chamber with viscoelastics when loose zonular support is suspected. Movement of the entire lens-capsule complex during anterior capsulotomy is always a sign of severe zonular laxity; the lens may be so loose that completion of the capsulorrhexis (CCC) by the usual means may be impossible because of lack of resistance and stability of the lens. However, the insertion of a retractor (iris or modified retractor) after the creation of an initial capsulotomy can provide a counterforce against which the CCC can usually be performed. Multiple grasps of the capsular flap may be helpful in overcoming the problem and completing the capsulorrhexis. CCC should be performed with the least possible downward pressure on the lens and avoiding any centripetal traction on the flap. The most obvious signs of zonular weakness include subluxation of the entire nucleus with visualization of the lens equator. However, mild zonular laxity resulting in the development of anterior capsule striae adjacent to the capsular flap during capsulorrhexis is more commonly seen. The location of these striae also indicates the weak region of the zonules. The CCC should be neither too small nor too large. Too small a diameter will add further stress to loose zonules during manipulation of the nucleus in the bag, whereas too large a diameter may engage the zonular attachments. The final capsulorrhexis size should be larger than that in nonXFS eyes, in order to reduce future shrinkage of the anterior capsule, due to the fibrosis produced by the remaining epithelial cells. Centripetal forces induced by anterior capsule contraction may aggravate zonular weakness and lead

to late dislocation of the intraocular lens (IOL) within the capsular bag.57,58

Hydrodissection and/or hydrodelineation must be performed carefully to avoid downward pressure on the lens whenever zonular fragility is suspected. Access to rotating the nucleus and epinucleus is important for performing the maneuver as gently as possible during surgery.59 However, the degree of dissection must be balanced against the fact that too aggressive an injection of fluid can lead to further zonular weakness. Alternatively, the entire nucleus should be hydrodissected and luxated anteriorly for supracapsular phacoemulsification to minimize zonular stress in XFS. However, in choosing this approach, care should be taken not to damage the endothelial cells.

Phacoemulsification and Cortex Aspiration

Phacoemulsification must follow the same principle of not stretching the zonulae. During surgery, extreme deepening of the anterior chamber at the onset of infusion may be indicative of zonular laxity. However, this phenomenon is more commonly seen in highly myopic eyes. It is generally advisable to perform phacoemulsification with a lower infusion pressure and, therefore, lower aspiration flow rate and vacuum levels in these eyes, although this will slow down the emulsification process. During sculpting of the nucleus, a tendency of the lens to move with the sculpted tip—that is, away from the surgical incision—is a clear sign of inadequate zonular strength. Ultrasonic power should be increased and stabilization of nuclear position by placement of a lens chopper, or a similar instrument, over the equator opposite the phaco incision to stabilize the position of the nucleus should be considered. During nucleus rotation, a tendency of the nucleus to return toward its previous location when released by the rotating instrument can be an ominous sign of zonular dehiscence. This indicates that the entire capsule has rotated somewhat with the nucleus, and subsequently returned to its normal anatomic location when the rotary force was discontinued. Therefore, rotation of the nucleus should be performed gently or even avoided, if possible. The surgeon should maintain centration of the nucleus during rotation with bimanual rotation, using both the phaco tip and a second instrument such as a phaco chopper or spatula whenever possible. Segmentation of the nucleus should be accomplished as gently as possible. Deep sculpting enables the nucleus to be cracked with less effort. Chopping techniques are preferred instead of the classic “divide and conquer” method, as all forces are directed to the center of the nucleus with minimal induced stress on the capsule and zonules.60 Finally, another sign of zonular deficiency, visible as nucleus volume decreases, is inward collapse of the lens capsule with possible inadvertent aspiration by the phaco tip.

Aspiration of the cortex is one of the steps that stress the zonules the most. After nucleus removal, tangential stripping of lens cortex from the capsular fornices may prevent further zonular dehiscence. In extreme circumstances, it may be necessary to position the distal end of a second instrument, such as a blunt spatula, against the capsular fornix to create counteraction as cortex is removed. At any time during cortex removal, peripheral posterior capsule striae may straddle an area of zonular dehiscence. The longest striae demarcate the area of dehiscence. Also, a forward shift of the posterior capsule caused by infusion fluid accumulation behind the posterior capsule (infusion misdirection) may occur. This phenomenon is more common in eyes with exfoliation and other causes of zonular laxity than in normal eyes.

can also be used to help prevent intraoperative posterior capsule rupture by keeping the posterior capsule taut, preventing its anterior bulging and protecting it from being aspirated by phaco or irrigation/aspiration tips during phacoemulsification and cortical aspiration.75 Finally, in theory, the CTR would counter the postoperative contraction of the anterior capsule, thus reducing shrinkage of the CCC and the risk of IOL dislocation. However, there is no real evidence to support this and several late dislocations with the IOL in the bag have been reported specifically in eyes with XFS.58 MorenoMontanes et al.76 described a useful surgical technique for removing the CTR after phacoemulsification in cases of posterior capsular rupture to prevent CTR dislocation into the vitreous cavity.

Modified endocapsular rings that can also be sutured to the sclera are available (e.g., the Cionni design)77 and should be used in eyes with more significantly loose zonules as they offer greater capsular stability and centration. Such rings contain a small strut with a distal eyelet (Fig. 15.4). Prior to inserting the ring, a double-armed 10-0 prolene suture can be passed through the eyelet. After ring insertion, both needles are passed through the appropriate region of the ciliary sulcus and tied to each other under a scleral flap to establish permanent positioning of the endocapsular ring and surrounding capsule.

Although the use of a CTR has been of great help to avoid complications due to loose zonulae, it does not always achieve lens stability and also may be hazardous, as its insertion can create further zonular damage. Nonetheless, expansion of the capsule sac is often desirable either during or after lens removal, and these devices enhance implant centration and reduce postoperative pseudophacodonesis.

Fig. 15.3 Photo of a Morscher MR 1400 capsular tension ring. Courtesy of FCI Ophthalmics, Marshfield Hills, MA

a

b

Fig. 15.4 Modified capsular tension rings: Cionni rings (a) MRiL and (b) M2L. Courtesy of FCI Ophthalmics, Marshfield Hills, MA